A Coalition government would toughen entry requirements for asylum seekers and provide mandatory prison sentences for people smugglers, Opposition Leader Tony Abbott says.

Mr Abbott used a speech to the Lowy Institute to reaffirm the Coalition's commitment to reopening the Nauru detention centre.

He said Australia should insist that asylum seekers carry documentation, and said he would give ASIO as long as it liked to carry out security checks.

He also pledged to tighten the current appeals mechanisms by restricting reviews to just one case officer, and "end taxpayer funding for further appeals".

Mr Abbott boasted of successful Howard government measures to stop boats, including turning them around.

He said when asylum seekers on the Tampa were denied entry to Christmas Island in 2001 and sent to Nauru, "people smugglers and their customers got the message and boat arrivals virtually ceased".

"In the aftermath of the Tampa incident, temporary visas, offshore processing, heightened cooperation with Indonesia and turning boats around denied the people smugglers a product to sell and all but stopped further arrivals," Mr Abbott said.

"There's every reason to think that what happened before can happen again, and that what was stopped before can be stopped again by making use of Nauru."

Mr Abbott said ASIO needs more than the current three months to carry out security checks as foreign partners "aren't influenced by Australian deadlines".

"Under the Coalition, ASIO would have as much time as it needed to establish whether those seeking protection visas represent a threat to our national security."

He said asylum seekers are required to have identity documents when they enter Malaysia or Indonesia on the way to Australia, but less than one in five people have them when they arrive on Christmas Island.

"Using existing powers, the Coalition would ensure that destroying or discarding documentation gave rise to a presumption against refugee status."

Clearance

Long delays in ASIO checks have resulted in asylum seekers waiting up to a year for a clearance. The delays have been blamed on the Christmas Island and Villawood riots this year.

But recent streamlining of the process has allowed Immigration Department officials, acting on an ASIO blueprint, to carry out the process quickly.

Out of 1,200 asylum seekers checked in March and April, only 200 were referred to ASIO for further scrutiny.

But a spokesman for Attorney-General Robert McClelland says there is still no time limit on security assessments.

He said they remain "rigorous" to ensure the protection of Australia's national interests.

Mr Abbott, meanwhile, says the Coalition would impose a mandatory one-year sentence for a people-smuggling first offence, and 10 years for a second.

However he pledged to increase refugee intake to 15,000, up from the 13,750 Australia admitted last year, through a private sponsorship scheme.

Even before Mr Abbott spoke, the Government demanded he ensure people aren't "left to rot" on Nauru, saying 120 people, including children, were locked up there for more than three years.

In a statement, Immigration Minister Chris Bowen and Home Affairs Minister Brendan O'Connor slammed the idea of towing boats back to Indonesia.

"How does he propose to tow back boats without risking the lives of those involved and where will he tow them to, considering Indonesia has said simply returning boats would be 'a backward step'?" the statement asked.

Mr Abbott will travel to Nauru this week to publicise his push to reopen the detention centre.